Patients with germ cell tumors which have recurred following conventional dose salvage chemotherapy will be treated with high dose chemotherapy and autologous bone marrow transplantation in this study. The high dose chemotherapy used will be carboplatin and etoposide. To increase the tolerability of marrow to etoposide administered post-transplantation, we propose to transduce peripheral blood progenitor cells (PBSC) with the Multiple Drug Resistance Gene-1 (MDR-1) at the time of stem cell collection. Our objectives are to determine if the transplantation of the transduced PBSC will lead to engraftment of these cells. Additionally, we aim to determine if post-transplantation chemotherapy will provide a selective advantage for MDR-expressing bone marrow cells. Finally, we will evaluate the safety of this retroviral mediated gene transfer.